I tried to analyse the Macaulay Culkin situation once. You know? Why he will always be young in our heads.

It's because he is a kid in Home Alone. We still watch it whenever we can and the actor hasn't appeared in many big projects after that.

Hence, our minds refuse to believe he has grown. Because we haven't seen it.

Macaulay Culkin in home alone
Source: The Indian Express

Now that I am done psychoanalysing the situation, let me tell you he is 40 years old now. 

Yes. This kid.

Kevin in home alone
Source: The New Daily

Is 40. 

Macaulay Culkin in home alone
Source: NME

And very self-aware. He posted a tweet on his birthday yesterday, and I can't stop laughing at the 'that's my job' bit.

He is also looking for some photoshop services, in case anyone is interested.

Now, no matter the mental preparation, this does come as a bit of a shock. Hence, the reactions:

These kids do grow up fast.